Trigger mechanism



A. c. PIERCE 2,533,283

TRIGGER MECHANISM 2 Sheets-Sheet 1 Dec. l2, 1950 Filed July 26, 1946ET'Iv l Dec. 12, 1950 A A. c. PIERCE TRIGGER MECHANISM Filed July 26,Y1946 2 Sheets-Sheet 2 gnam/Mofo AU] ETJL E. Fie-rl: E

MQMMMMW M Patented Dec. 12, 1950 UNiTi. Sid

FICE

1 Claim.

(Granted ander the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) The invention described herein may be manufactured and usedby or for the Government for governmental purposes without the paymentto me of any royalty thereon.

This invention relates to an automatic lirearm and more particulariy toa trigger mechanism whereby an automatic iirearm may be fired twodifferent rates of automatic lire and semiautomatically as well.

In the Browning automatic rifle as described in Browning Patent No.1,293,622, a rate reducing mechanism therefor has been evolved toproduce a slow rate of automatic fire in addition to the normal hi-ghrate ci fire. Such rate reducing mechanism is fully explained in il. S,Fatent No. 2,379,461 to Clarence E. Simpson. The safety feature of thebasic firearm of course, been unchanged and functions in the usualmanner. However, this rate reducing mechanism has eliminated theprevious feature of semi-automatic lire.

It has been found that in certain tactical situae tions single shot ireis highly desirable. For instance, the operato-r of the firearm may wishto hide from the enemy the fact that an automatic weapon is present andwhen attacked can com bine the element of surprise and the fire power ofthe weapon to beat oli such attack.

Without this invention a d extrous operator may be able to lire singleshots 4".i'fith the selector set at the slow rate of ire, but auchoperation requires expert manipulation oi the trigger finger. an artwhich usually presents consider able diculty to an inexperiencedoperator.

It is therefore the purpose of this invention to change the existingrate reducing mechanism in a Browning automatic rifle so as toincorporate semi-automatic, or single shot nre in addition to the othertwo rates of automatic ire.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawings in which:

Fig. 1 is a fragmentary elevational View of the operating section of agun in partial longitudinal section showing semi-automatic position ofthe trigger mechanism prior to pulling the trigger.

Fig. 2 is a View similar to Fig. i but showing the trigger mechanismafter the trigger has been pulled sufiiciently to release a slide.

Fig. 3 is a fragmentary elevational View ci the trigger mechanism inlongitudinal section showing the position of the assembly after thetrigger has been pulled fully to the rear.

Fig. 4 is a top elevational view of the change lever.

Fig. 5 is a side view of the change lever shown in Fig. 4.

Fig. 6 is an enlarged view taken along line 6 6 of Fig.. 5.

Fig. '7 is an enlarged view taken along line -l in Fig. 5.

Fig. 8 is a perspective View of the trigger and connector assembledthereto.

Fig. 9 is a perspective view of the sear spring.

Fig. i0 is a perspective View of the sear.

Fig. il is a fragmentary elevational View of a portion of the gun in theregion of the trigger housing showing the markings on the receiver forthe various settings for the trigger mechanism.

The operation of the Browning automatic rifle and the added features ofthe rate reducing mechanism are contained in the patents to Browning andSimpson respectively mentioned above. For the purposes of this inventionreference will be made only to those parts and functions as are hereconcerned.

The operation of the nrearm with which this invention is concerneddepends on a movable slide. If such slide is free to reciprocate, arapid rate of automatic lire is produced. But if the slide ismomentarily halted in its reciprocating travel by a sear, a slow rate ofautomatic nre is obtained. In order to secure semi-automatic orsingle-shot re, the slide obviously must be retained by the Sear untilsuoli time as the trigger is again pulled. The method by which suchaction of the sear and slide can be obtained will be explained below.

A trigger 2 is pivoted at its forward end between the walls of a triggerguard 3 by a pin S. The rear top end of trigger is slottedlongitudinally as shown at i in Fig. 8, and the metal cn each side ofslot 'i forms two shoulders 8 for a purpose to be explained.rl'ransversely disposed within slot 'l is a pin 9 which serves to seat aoonnector lil.

Such connector ts loosely within triggel` slot 'l and is shaped in theform of a boot with a heel Il and a toe l2. The portion of connectol` l0which may be termed the instep i3 pivotally engages pin 9. The upperportion of connector lil extends above trigger shoulders 8 and has anarrow lat head i4 and a cam surface i5 on the back side of connectorl!) sloping downwardly and rearwardly for a purpose to be explained.Another inclined surface I6 slopes downwardly and forwardly from headi4. A sear spring (Fig. 9) of the flat type is mounted in longitudinalgrooves (not shown) in the sides of trigger guard 3 and is secured inposition by the forward end thereof engaging a transverse slot i9 intrigger guard 3. The rear portion of sear springy il consists of threetongue-like leaves, two similar outer leaves 2t and a short middle leaf2 l.

A sear carrier 22, having a vertical longitudinal slot 24 providedtherein and opposed transverse longitudinal slots (not shown) in theforward end of the side walls thereof, is slidably mounted withintrigger guard 3 for limited longitudinal movement on trigger pin 6. Atransverse pin 23 is mounted towards the rear of slot 24 with the endsprotruding equidistant from both sides of sear carrier 22 which areslidably mounted in opposed transverse longitudinal slots (not shown) inthe walls of trigger guard 3. A forward portion 36 of sear carrier 22 isdiametrically shaped to accommodate a helical spring 58. The front endof spring i8 is seated against the forward inside wall of trigger guard3 and provides bias tocarrier 22 to absorb the blow on counterrecoil ina manner described in the first mentioned patent referred to above. Theupper portion of trigger 2 and the connector i@ both lie within thelongitudinal slot 2G in sear carrier 22.

Transversely disposed within slot 2B is a fixed pin 25 which lies infront of connector lil and limits the forward movement thereof. On theunderside of sear :carrier 22 at the rear end of slot 2li is an upwardlyinclined surface 2t, which mates with kand cams connector iii in amanner to ce explained. y

Pin 23 is also used to pivotally mount a sea-r 21 and a sear releasestop lever 28. As shown in Fig. lil, sear 2 has a rearwardly extendingnose 29 and a bifurlcated rear end 3Q having upwardly inclined camsurfaces 3l. The forward end of sear 2l terminates in two outwardlyextending flat ears 32. Sear release stop lever 258 lies within a slot33 in sear 2 and the forward end of lever 28 terminates in a downwardlyprojecting tip 34. The rear portion of lever 28 extends upwardly frombeneath sear 2l into the ibifurcated rear end 'Sil and protrudes.rearwardly beyond cam surfaces 3|.

A spring 35 of the at type is mounted in longitudinal grooves (notshown) at the rear of trigger guard 3 and is retained in position by therear end engaging a transverse groove 3l in trigger guard 3 in a mannersimilar to that of Sear spring il. A rearwardly and upwardly extendingtongue 38 on spring 35 abuts the underside of the rear portion of lever28. A forwardly extending portion of spring Y35 terminates in a curvedtoe 39 which cooperates with a change lever lo to obtain the differentpositions for the classes of operation of the rilie.

Change lever 4e consists of a cylindrical bar 4l transversely mounted intrigger guard s from the left side thereof as shown in Fig. 1l. Aprojecting lug e9 on bar il limits the lateral displacement of changelever d when inserted in trigger guard 3 and is retained in ,positionbetween the inner surface of the further wall thereof and a clearancecut (not shown) on the outer right side wall of scar carrier 22. One endof bar il terminates in a perpendicularly disposed arm $2 which servesas a handle for effecting rotation of change lever lill. Four shallowlongitudinal grooves 53 are cut on the periphery of bar ill, so disposedas to be on top thereof when arm 2 is held in a vertical .position withthe arm pointing upwards. The forward side of bar lll is slottedvertically as shown at in Figs. Lligand A in such a way as to .leave alittle tongue of metal. Such tongue is then bisectecl by a longitudinalgroove 41 so as to leave a projecting lug at the top and bottom betweenvertical slots All. The arm 42 of change lever 4U extends upward whenassembled to the trigger guard 3 along the left side of receiver 4 onwhich is marked the positions F for slow rate of automatic lire, SA forsemi-automatic lire, A for rapid rate of automatic fire, and Si forsafety in clockwise order as shown in Fig. 1l. The cuts and lugs onchange lever bar fil control the action of the trigger 2 and connectorl0 giving the fclasses of lire mentioned above.

At the start of the cycle for semi-automatic fire, a reciprocable slide5 is held to the rear by the engagement of sear nose 29 with a searnotch @8 in the underside of slide 5. Change lever el) has been rotatedto the position for semi-automatic fire indicated by AESA on the leftside of receiver e. The toe Se of change lever spring 35 at this timeengages the uppermost longitudinal groove 153 in change lever t toprevent the possible rotation thereof against the jar of the recoilingparts into an adjacent groove which would effect a different class ofiire. When trigger 2 is pulled rearwardly, such trigger pivots upwardlyabout trigger pin B thereby raising connector i@ against the bias of themiddle leaf y2|- of sear spring Il. The flat head lf3 of connector i@therefore contacts the underside of the forward edge of sear 2l. Thusconnector lil serves as an auxiliary means whereby the movement oftrigger 2 effects the release of slide 5 through the medium of sear 27.

Continued pressure on trigger raises `con nector Eil higher, causingsear 2i to pivot about sear ier against the bias of scar spring outerleaves which press down on ears .32 of scar El. At this time shoulders son trigger Z enter slots substantially as shown in Fig. Y2. As the frontend of Sear i pivots upwardly, sear nose 29 drops from engagement withSear notch d all-owing slide E to go forward under the action of recoilspring (not shown) to fire a :cartridge in the manner typical of theBrowning automatic rifle.

Further pressure on trigger 2 causes connector head Mi to rise evenhigher to a point where connestor lil begins to be cammed forward by thesear carrier cam surface 2S. At this point trigger shoulder 3 Ybottomsin longitudinal groove i? across change lever slots Ml therebypreventing any further upward travel of connector it.. As connector iscammed forwardly, head slips out from under the .front end of scar 2lpast projecting tip 3ft of scar release stopl lever 28, and theconnector front cam vsurface it raises sear spring middle leaf 2l. SinceSear releases stop lever 2t is not here contacted by connector suchlever es remains in the unpivoted position with the rear portion thereofprotruding beyond cam surfaces 5l on the rear end of Sear 2?. rifliuswhen sear 2'? returns to the u-npivoted position under pressure of theouter l-eaves 2S of Sear spring Ei, a sear release 5@ cannot strike camsurfaces 35 to pivot scar again to release slide E as in slow automaticlire. The upraised tongue Se of change lever spring 35 keeps searrelease step lever 23 from pivoting in semi-automatic fire due to thejar given the gun by the recoiling parts thereof. With Sear 2l' in thenormal position, as shown in Fig. 3, sear nose 29 is obviously onceagain in a position to engage Sear notch it in slide thereby assuringthat but one shot is red. As trigger v2 is released prior to firing thenext shot the downward bias of sear u spring .middle leaf 2l urges thereturn of connector i9 to the pre-tiring position shown in Fig. 1.

It should be understood that the parts of this invention also providefor slow and fast automatic re as well as a safety position which aredescribed in the Simpson patent referred to herein. However thisinvention provides the additional feature of semi-automatic re asexplained above.

Thus there is here provided a means for o'otaining semi-automatic nre ina Browning automatic rifle merely by selecting the proper position for aselector lever.

I claim:

`In Yan automatic firearm having a trigger slotted to form a pair ofbifurcated shoulders, a slide reciprocabley between a recoiled and abattery position, a pivotal sear arranged to engage and retain the slidein the recoiled position, reciprocable sear release means operative onthe rear end of the Sear for pivoting the latter to disengage from theslide, a stop lever jointly pivoted with the sear and normallypositioned to block the Sear-actuating movement of the sear releasemeans and resilient means for returning the sear and the stop lever totheir original unpivoted position, the combination of, an auxiliarymember pivotally carried by the trigger and operative on the front endof the sear for pivoting the latter to disengage from the slide, arotatable member transversely mounted in the rearm and having anoutwardly projecting handle portion, said member having fourlongitudinal spaced grooves about the periphery thereof and a cutawayportion intersecting two of said four grooves, said cutaway portionbeing formed by a pair of slots substantially parallel to the verticalaxis of said handle portion and a groove medially connecting said slotsand of increased depth relative thereto, and means for selectivelypositioning said rotatable member with any one of said four longitudinalgrooves in the uppermost poSition whereby three different classes offire and a safe position are individually obtained upon actuation of thetrigger, said cutaway portion being inclined relative to the vertical soas to permit the trigger shoulders to bottom therein when said rotatablemember is located with said third peripheral groove in the uppermostposition, said auxiliary member being constructed and arranged so as topivot suiiciently forward upon actuation by the trigger to bypass thefront end of the stop lever whereupon the rear end ofthe lever will bein position to block the sear-disengaging movement of the sear releasemeans and thereby produce semi-automatic re in that another cycle oftrigger actuation is required to again release the sear from therecoiled position.

ALBERT C. PIERCE.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS

